Coil structure



L. MAUERER COIL STRUCTURE Nov. 9, 1943.

Original Filed June 2, 1939 Patented Nov. 9, 1943 con. STRUCTURE LeopoldManerer, Chicago, Ill., assignor to Jefferson Electric Company,Bellwood, 111., a corporation of Illinois Original application June 2,1939, Serial No. 277,044. Divided and this application June 23, 1941,Serial No. 399,315

7 Claims. (Cl. 175-21) This invention relates to a coil structure, andmore particularly to a coil structure having a thin winding section anda high ratio of window length to overall length which is particularlywell adapted to use as a scanning yoke for television receivingapparatus in association with a cathode ray tube, and in televisioncameras on the camera tube.

Although other uses may be or become apparent for the coil assemblydisclosed herein, the illustrated adaptation thereof is particularlyadapted to television apparatus.

This application is a division of my copending application Serial#277,044, filed June 2, 1939, Patent No. 2,269,678, granted January 13,1942.

It is an object of this invention to provide a coil assembly forcontrolling the deflection of the electron beam of a cathode ray tube,which coil assembly has improved magnetic efliciency brought about bythe reduction of the high reluctance air gap between the coils thereofand the cathode ray tube.

Another object of this invention is to provide a coil assembly, thecoils of which have axially thin end sections so that the coil windowlengths are long as compared to the available space for the coils in thedirection of the longitudinal axes thereof.

Another object of this invention is to provide a coil assembly includinga plurality of coils, the magnetic axes of which are at right angles,and in which the coils are self-locating in their proper positions forsuch angular relations. Another object of this invention is to provide ascanning or deflecting yoke for use with a cathode ray tube intelevision apparatus in which the efnciency is improved by utilizingcoils of such size and proportion that the sides thereof surround theentire circumference of the cathode ray tube.

Another object of this invention is to provide a coil assemblycomprehending prewound and subsequently assembled and deformed coils.

Another object of this invention is to provide a. scanning yoke assemblyfor use with television apparatus including a cathode ray tube whichproduces a magnetic field which is substantially uniform over the entirecross sectional area that is traversed by the beam in the tube.

Another object of this invention is to provide a scanning yoke assemblyfor use with the oathode ray tube in television apparatus, in whichassembly the longitudinal axes of the coils are substantially parallelto the longitudinal axis of the cathode ray tube.

Another object of this invention is to provide acompact and eillcientmagnetic scanning yoke for use in television receivers or transmitterswhich utilize a cathode ray tube for reproducing television pictures oron a camera tube for producing pictures.

Another object of this invention is to provide a magnetic scanning yokefor television apparatus which may be easily and consistentlymanufactured in production quantities;

Further objects and advantages of the present inventionwill be apparentfrom the following description, reference being had to the accompanyingdrawing wherein a preferredembodiment of the present invention isclearly shown.

In the drawing: 1

Figure 1 is a side elevational view showing an adaptation of a preferredembodiment of this invention to television apparatus;

Figures 2 and 3 are respectively perspective and end views of apreferred embodiment of this invention;

Figure 4 is a side elevational view of the coil shown in Figures 2 and 3with a portion cut away to show certain structural details; and

Figures 5 and 6 are fragmentary sectional 7 views indicatingmodifications of this invention.

r In Figure 1 a scanning yoke [0 made in accordance with this inventionis shown applied to a cathode ray tube H, in conjunction with which itis adapted to operate as a part of television receiving apparatus. Thecathode ray tube II is one of the type commonly in use for the purpoesspecified and has a glass envelope l2 and a fluorescent screen at oneend, as at l3. The tube il includes an electron gun, the end of which isindicated by dotted lines at It, and from which an electron beam isprojected against the fluorescent screen at l3. The wall ll of the tubeadjacent the fluorescent screen I3 flares outwardly to permit deflectionof the electron beam over a greater fluorescent screen surfaces. A neck#5 of the envelope l2 encloses the electron gun M and extends a distancebeyond the end of the gun. A base I6 is secured to the end of the neckl5 and has prongs l7 secured thereto to which the electrical connectionsare made to theinternal elements of the tube. A terminal 18' is securedto the envelope for making an electrical connection to a high voltageelectrode or anode of the tube.

. The scanning or deflecting yoke 10 preferably fits closely around theneck I5 of the envelope l2 and preferably extends from the end of thegun It to the portion of the envelope where the spect to each other thattheir magnetic axes are' perpendicular. It is also preferable andparticularly desirable that the longitudinal axes of the coils areparallel to the electron beam in its normal or undeflected position. Themagnetic axes of the coils l3 and 20 extend across the neck I5 of thetube and are substantially perpendicular to the longitudinal axis, ofthe tube as well as the normal or undeflected beam. In order to improvethe magnetic efllciency of the scanning or deflectingyoke l0, it isparticularly desirable that the high reluctance air path between thecoils and the envelope is minimized. Also, a low reluctance magneticflux path 22 closely surrounds the outer surfaces of the coils andextends circumferentially around the neck l5 of the tube. As will bemore fully explained, it is desirable that the window openings of thecoils are as long as possible with respect to the space available forthe scanning or deflecting coil assembly between the end of the electrongun It and the outwardly flaring portion of the envelope l2. Thisfeature provides a greater effective length of the coils in the spaceavailable therefor. In addition to being desirable from the standpointof magnetic efficiency that the distance between the coils l9 and andthe envelope I2 of the tube is minimized, it is also desirable that theair gap or leakage space between the low reluctance magnetic return path22 and the envelope I2 is also minimized. This reduces the reluctance ofthe magnetic path over which there is possibility of control, since themagnetic path through the tube is flxed by the dimensions of the tube.The previously mentioned features of construction of the scanning ordeflecting yoke In, as well as the features of construction and assemblywhich provide a yoke consistent with the features will be more fullyunderstood in considering the detailed description of structure whichfollows.

In the structure of the disclosed coil assembly, a form 23 of phenolfiber or other suitable insulating material provides a cylindricalsupport for the coils l9 and 20. The form 23 preferably has an internaldiameter such that it fits snugly around the neck l5 of the cathode raytube ll. Also, the wall of the form 23 is preferably thin so that thelength of the flux path therethrough .is minimized; although, of course,it must be sufficiently thick to provide a support having amplerigidity. In referring to the cylindrical characteristics of the form,it is understood that while a circular cylindrical form is preferable,the term cylindrical as used herein covers forms having polygonalsections.

The coils l3 and 20 are so disposed with respect to the form 23 that thesides of the coils .9 and 20 are substantially parallel to thelongitudinal axis of the form. This makes the longitudinal axes of thecoils parallel to the longitudinal axis -of the form and consequentlymakes the longitudinal axes of the coils parallel to the electron beamof the cathode ray tube when that beam is in its normal or undeflectedposition and the scanning or deflecting yoke It is properly mounted onthe tube. The coil sides which are adjacent the form are axiallystraight and sectionally conform to the outer surface of the envelope.The transverse disposition of the coils is such that their magnetic axesare perpendicular. Several assasoe advantages are gained by making thecoils of such a width that the circumferential spread of the sides ofone of the coils is substantially equal to the width of the window ofthe other of the coils. That is, the design of the coils is preferablysuch that the coil sides of each of the coils clrcumi'erentially coversone-fourth of the surface of the'form 23 or the coil sides are soproportioned in any event that the coil sides of each of the coils fltinto the windows of the other of the coils. Some of the advantages whichare attendant with this construction are:

(a) That the coils l3 and 20, when secured in position, naturally andautomatically space themselves in such positions that their magneticaxes are perpendicular;

(b) The windings are spread over the entire circumference of the form sothat a maximum number of turns can be put into a minimum of radialspace;

(0) The magnetic efficiency of the yoke is improved by minimizing theradial air space required by the coil sides;

(d) The distribution of the magnetic fleld is substantially uniform overthe entire cross sectional area of the cathode ray tube which istransversed by the electron beam in that tube; and

(e) Inconsistencies of manufacture of the yokes in quantity productionare limited.

In the flnal assembled form of the yoke H), the end turns of the coil l8and 20 extend outwardly from and circumferentially around the ends ofthe form 23; half of th end turns of each coil extending around one sideof th form 23; and the other half of the end turns of each coilextending around the opposite side of the form 23. As indicated in thedrawings, half of the end turns of the coil l9, indicated at 24 and 25extend around one side of the form 23 and the other half of the endturns of the coil l9 indicated at 26 and 21 extend around a portion ofthe form 23 diametrically opposite the end turns at 24 and 25. Likewise,the coil 20 has half of its end turns, as at 28, extending around oneside of the form 23 and the other half of its end turns extending aroundthe diametrically opposite side of the form, as at 29 and 30.

The end turns such as 24, 25, 25, 21, 28, 29 and 30 of the coils l9 and20 are preferably so relatively disposed that they extend radiallyoutwardly from the form 23 and have a section which is axially thin. Theend turns of half of the turns of each of the coils extend arounddiametrically opposite halves of the form 23. The

thin axial section of the end turns which is particularly desirableprovides coil windows which are axially long as compared to the overallaxial length of the finished coils l9 and 20 and the overall length ofthe finished yoke. The ratio of axial window length to the yoke lengthshould be high to provide windows which are as long as possible in thespace available for the yoke. As indicated in Figure 1, the spaceavailable for the yoke is that between the end of the electron- Althouzhthe coil assembly may be impregnated with wax or some similar substanceto help to hold the turns thereof in their assembled pomtions. thisprocedure is not particularly necessary when the coils are assembled ona form such as 23. The coils l9 and 23 are held in position with respectto the form 23 by a wrapping of an adhesive tape such as 32 which may ba cellulose tape. Also, to strengthen the end turns and better to securetheir positions, wrappinzs of an adhesive tape, such as cellulose tape,surround the end turns 24, 25, 26, 21, 28, 29 and 30, as at 33, 34, 35,36, 31, 38 and 39 respectively.

As illustrated. in Figure 4, the low reluctance magnetic flux path 22which surrounds the windings of the coils l9 and 20 preferably comprisesa plurality of layers 40 of magnetic wire wrapped circumferentiallyaround the coils and having the layers 40 separated by paper 42 or othersuitable insulating material. The low reluctance path 22 provides areturn path for the fiux of the coils i9 and 2B which passes through thecathode ray tube II to effect deflection of the electron beam. Since theinternal diameter of the form 23, and the consequent length of the airgap within the form 23, is determined by the diameter of the neck l ofthe cathode ray tube, the length of that portion of the flux path isdetermined. However, the magnetic efiiciency of the yoke is improved byminimizing the space between the low reluctance path 22 and the insideof the form 23. By utilizing the entire outer surface of the form 23 forwinding space and eliminating gaps between the windings, a greaternumber of turns are wound in a given radial space to reduce the lengthof the air gap outside of the cathode ray tube and improve magneticefilciency. It is important also, from the standpoint of minimizing theradial space required by coils i9 and 20, that the space factor of thewindings themselves be kept high.

In the yoke illustrated in the drawing, each of the coil windings ofeach of the two coils i9 and 26 covers approximately one-fourth of theouter surface of the form 23. The sides of each of the coils areapproximately the same width. It is understood, however, that the sidesof one of the coils may be made wider than the sides of the other coil,but in such proportion that the sides of the two coils abut and coverthe surface of the form 23. Such distribution of the coils on thesurface of the form gives a distribution of the windings and theirmagnetic fields which are comparable to the picture proportions commonlyutilized in television apparatus, as for example the proportions of 3 to4.

In the modified structure disclosed in Figure 5, the coils i9 and have aplurality of layers; the coil i3 having layers such as 43 and 44.Although it is understood that the coils of any of the various formsdisclosed may have either one or a-plurality of layers, the particularform disclosed in Figure 5 has a part of the layers, such as the layers43 of the coil l9 and the layers 45 of the coil 20, which are ofsubstantially the same width as, and fit into the window of the othercoil to cover the entire circumference of the form 23. These layers 43and 45 accomplish the spacing of the windings upon the form and theself-alignment and positioning of the coils l9 and 20. The other layers,such as 44 and 46 of the coils are so distributed that they provide adesirable distribution of the magnetic fields of the coils. With thelayers 44 and 43 distributed intermediate the edges of the coils l3 and20 respectively, a type of distortion known in the art as "barreldistortion is obtained. This particular type of distortion is utilizedin compensating for a characteristic of some cathode ray tubes. Thisdistortion would normally tend to cause the sides of the image patternto bulge or be convexly distorted from the normal or undistortedpattern. Although the inherent spacing alignment of the coils is notattendant with the spacing of the sides of each of the coils, one fromthe other, it is understood that other struc tural features of the yokemight be utilized with the coil sides spaced apart or separated on theform 23.

In the modified structure illustrated in Figure 6, the sides of one ofthe coils overlap the sides of the other coil as illustrated at 41 and48 where the sides of the coil l9 overlap the sides of the coil 20. Theoverlapping of the coils in this manner provides a form of distortionwhich is known in the art as pincushion distortion. This type ofdistortion is sometimes desirable to compensate for other variations andcharacter istics of the cathode ray tube.

In all of the forms of the yoke l0 which have been described herein, thesides of the coils i9 and 23 are preferably continuous, but it isunderstood that the halves of the coils may be separately wound, andthen assembled and connected together. It is also a feature of thedesign and structure disclosed herein that yokes similar to thosedisclosed may be made on a removable form, supported by an impregnationor coating of wax or other suitable insulating material and the formthen removed from the finished structure.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

Whatis claimed is:

1. A coil assembly comprising, in combination, a pair of coils havingside portions and end portions and window openings defined by saidpertions, portions of the coil turns comprising the side portions beingsubstantially parallel and together defining a cylinder having an axissubstantially parallel to said side portions, the side portions of eachof the coils being of substantially the width of and fitting into thewindow openings of the other of the coils, and the end portions of thecoils extending radially about said defined cylinder.

2. A coil assembly comprising, in combination, a pair of single layercoils having sides and ends and window openings defined by said sidesand ends. the portions of the coil turns comprising the sides beingsubstantially parallel and defining a cylinder, each of the sides ofeach of the coils covering substantially one quarter of thecircumference of the defined cylinder and means securing the coils inposition.

3. A coil assembly comprising, in combination, a cylindrical form, apair of multi-layer coils having sides and ends and windows defined bythe sides and ends, the turns of the sides being relatively disposed todefine a cylinder and extending longitudinally of the defined cylinder,at least one of the layers of each of the sides of one of the coilsbeing of substantially the width of and fitting into a window of theother coil, and means securing the coils in position.

4. A coil assembly comprising, in combination,

a pair of multi-layer coils having sides and ends and windows defined bythe sides and ends, the turns oi! the sides being relatively disposed todefine a cylinder and extending longitudinally of the defined cylinder,at least one of the layers 01 each of the sides oi one of the coilsbeing of substantially the width of and fitting into a window of theother coil, the remaining layers of each of said sides of said coilsbeing narrower than the window width of said other coil andsymmetrically spaced with respect to other layers, and means securingthe coils in position.

5. A coil assembly comprising, in combination, a pair of coils havingsides and ends and windows defined by the portions of the coil turnscomprising the side portions and ends, the sides of said coils beingsubstantially parallel, said coils being disposed with their magneticaxes substantially perpendicular, and -the sides of one coil being orsubstantially the width 01' and fitting into the windows of the othercoil.

6. A magnetic deflecting yoke for a cathode ray tube comprising a pairof coils each having side portions and end portions defining windows,each of said side portions being shaped to define a longitudinal sectionof a cylinder, the turns of the side portions of each coil extendinglongitudinally of and being spread over said defined cylindrical sectionso as to occupy the minimum of radial space, the side portions or onecoil being so dimensioned and arranged as to seat in the windows of theother coil so that together all the side portions or said coils define acomplete cylinder and upon assembly the axes or said coils automaticallyare arranged substantially perpendicularly to each other, the endportions of said coils extending in partial overlapping relationoutwardly and radially from and about'said defined cylinder vto produce-a high ratio of window length to overall length. w

7. A magnetic deflecting yoke {(111 a cathode ray tube comprising a pairof coflsfeach having side portions and end portions defining windows,

each of said side portions being shaped to define a longitudinal sectionof a cylinder, the turns of the side portions of each coil extendinglongitudinally of and being spread over said defined cylindrical sectionso as to occupy the minimum or radial space, the side portions of onecoil being so dimensioned and arranged as to seat in the windows of theother coil so that together all the side portions of said coil define acomplete cylinder and'upon assembly thev axes of said coilsautomatically are arranged substantially perpendicularly to each other,the end portions of said coils extending in partial overlapping relationoutwardly and radially Irom and about said defined cylinder to produce ahigh ratio of window length to overall length, and a low reluctancemagnetic return path comprising a plurality of layers of magneticmaterial insulated from each other and extending circumferentiallyaround the side portions between the end portions of said coils.

LEOPOLD MAUERER.

